"The section continues to provide expert physical and technological support for radiation treatment, consisting of routine calibration, quality assurance and first-line maintenance of all radiation producing and ancillary equipment. It includes special dosimetry studies, computer- assisted treatment planning, patient monitoring and the design and development of special equipment tailored to developing clinical needs. Diodes are now in routine clinical use for the verification of patient doses and exhibit an accuract of +/- 3%. The 6 MV accelerator has been installed. The radiosurgery system has been installed and commissioned. We have successfully treated 6 stereotactic radiosurgery patients so far. The project in collaboration with the Naval Research Laboratory to evaluate the clinical utility of semiconductor doped Vycor is well under way. We are in the process of characterizing dosimetric properties and using this to refine detector development. Clinical trials are expected to start by early Summer, 1999. Ongoing projects are the commisioning of a refined stereotactic treatment planning system capable of treating more complex tumor volumes, the installation and commissioning of the mini-multileaf collimator, and the edevelopment of intensity modulated radiation therapy (IMRT) with the establishment of an IMRT research program at NCI and the development of a frameless stereotactic localization system."